(1) Field of the Invention
The present invention relates to a solid pole oxygen sensor, and more particularly to a solid pole oxygen sensor which is to be set in an automotive exhaust system to detect the oxygen concentration in the exhaust gas, and to a process of manufacturing such a solid pole oxygen sensor.
(2) Description of the Prior Art
An oxygen sensor is a device for measuring the equilibrium oxygen partial pressure in a gas to be measured and it is conventionally constituted such that internal and external electrodes of platinum or platinum family alloy film are formed inside and outside of a solid electrolyte vessel made of a solid electrolyte such as zirconia which is usually stabilized with, for instance, yttrium oxide. The vessel is filled with air (gas) of a solid substance with a constant equilibrium oxygen partial pressure, for instance, a mixed powder of metal-metal oxide as the internal reference material; and thereby the equilibrium oxygen partial pressure of the gas to be measured can be detected by converting the ratio of the equilibrium oxygen partial pressures between the gas and the internal reference material to an electromotive force. As the internal reference material, gases and solids are available. However, because the oxygen sensor is to be positioned in an automobile, a solid is found more advantageous from the standpoint of physical properties and structure.
The conventional solid pole oxygen sensor, which requires calcinating or high-temperature firing of the solid electrolyte vessel in its manufacture, is troublesome. It is too complicated structurally to be reduced in dimensions. Moreover, it is difficult to take out the potential of the internal electrode in the solid electrolyte vessel.